1. Field of the Invention
The present invention relates in general to an intravenous or intra-arterial catheter-cannula assembly and more specifically concerns a catheter-cannula assembly that reduces the back flow of fluid through the assembly.
2. Description of the Prior Art
Intravenous and intra-arterial catheter-cannula assemblies are well-known in the prior art and are employed to deliver drugs, fluid or blood to a patient or for blood sampling. Such assemblies are utilized by insertion into a patient's vein or artery in combination with an introducer needle. Generally, the needle seats inside the catheter-cannula as a unit and is inserted into the patient's vein or artery. After the combined catheter-cannula and needle are properly positioned, the needle is then withdrawn and an intravenous infusion set or other appropriate device is connected to the end of the catheter-cannula for delivering fluid to the patient.
In making the infusion set hookup, there is often a problem of blood flowing through the catheter-cannula and out its hub end during the connection process, especially during arterial cannulation. In this age of deathly consequences resulting from contamination by blood-borne diseases, it is imperative that such back flow of blood through the catheter-cannula be avoided as much as possible.
Various types of devices have been developed for preventing the back flow of blood through the catheter-cannula. Most of the prior efforts, however, have been made by sealing the catheter-cannula with an elastomeric seal of some type or reseal plugs that allow penetration by a needle and are then resealable. Clamping devices have also been disclosed in the art that serve to provide a clamping of the catheter tubing as described in U.S. Pat. No. 4,198,973. Other devices for sealing the hub are the use of ball valve assemblies such as disclosed in U.S. Pat. No. 4,261,357. Various wing type cannula devices have also been proposed as indicated in U.S. Pat. No. 4,006,744.
None of the prior art devices described above have been fully satisfactory in preventing the back flow of blood and contamination when catheter-cannulas have been used. The present invention provides an improved method for achieving this objective and does so with a construction that is relatively simplistic and yet efficient.